The invention generally relates to an inflatable seat belt.
In a three-point seat belt of this type, known from U.S. Pat. No. 5,474,326 A, an internal air tube is provided which forms a gas channel for filling the inflatable shoulder and pelvic belt parts. In the non inflated state, the air tube is collapsed so the inflatable seat belt has the form of a flat strip. There is a risk of the collapsed air tube being kinked in the eyelet of the buckle tongue at the deflection point of the seat belt located between the shoulder belt part and the pelvic belt part, so that the shoulder belt region cannot be filled or can only be filled with difficulty.
Measures for increasing the volume of the seat belt in the region of the deflecting eyelet are provided in the region of the deflecting eyelet on the buckle tongue in U.S. Pat. No. 5,383,713 A. No measures are provided on the known seat belt, however, which allow a continuously open gas channel between the shoulder belt region and the pelvic belt region for reliable filling of the belt interiors.
With a three-point seat, known from U.S. Pat. No. 5,390,953, the filling gas is supplied via the buckle and the plug-in tongue inserted into the buckle during application of the belt. This supply of gas from the plug-in tongue to the pelvic belt part and chest belt part necessitates fastening the plug-in tongue on the belt webbing. Adaptation to occupants of different sizes therefore necessitates additional expenditure in the form of a belt retractor at the respective end of the shoulder belt part and pelvic belt part.
In the seat belt known from U.S. Pat. No. 3,929,205, a fastening eyelet is fastened in the transition region, in which pelvic belt part and shoulder belt part converge, by stitching the two converging belt parts to the belt webbing. Adaptation of shoulder and pelvic belt part to different sizes of vehicle occupant is also achieved here by means of belt retractors provided at the respective ends of the shoulder and pelvic belt parts. A continuously open gas flow connection between the belt interiors of the shoulder belt part and pelvic belt part is created between the two belt parts by a hose guided next to the stitching. The gas is supplied via the hose which extends through the shoulder belt part. For this purpose, the hose is deflected round a deflection point provided in the region of the belt retractor at the upper end of the backrest. A weight is provided for achieving taut hose guidance during application and removal of the seat belt.
The seat belt known from U.S. Pat. No. 3,975,258 consists of a hose material which forms a continuous internal space for the individual belt parts. During normal operation, a vacuum is produced in the interior of the belt in order to obtain a flat belt shape. Springs surrounding the hose material enable the belt to be brought into the hose shape and air is supplied for filling the hose when the vacuum is removed, for example as the result of excessive deceleration of the vehicle.
The three-point seat belt known from U.S. Pat. No. 3,682,498 is formed statically without a belt retractor. The chest/shoulder belt region and the pelvic belt region are supplied with filling gas via a common valve point from a compressed air bottle. Belt parts which reduce the contact pressure of the seat belt on the vehicle occupant and also provide protection from impacts by parts of the vehicle such as steering wheel, dashboard and the like are to be inflated in the chest/shoulder belt region and pelvic belt region. The way in which the seat belt is attached to the vehicle body when applied on the buckle side is not shown in detail.
EP 0 366 518 A1 also discloses an inflatable three-point seat belt which is integrated into a vehicle seat and in which the gas for the filling gas is supplied at an end of the pelvic belt part connected to the end fitting provided on the vehicle body. The pelvic belt part is filled first of all, and the filling gas is then conveyed round a deflection point provided in the other end region of the pelvic belt in order also to fill the chest/shoulder belt region. In order to create a flow of gas through the deflection point during the filling of the two belt regions, the belt webbing is held at this point in a special guide at the end of the pelvic belt part on which a buckle is normally provided. The special guidance or mounting of the deflection point between pelvic belt part and chest/shoulder belt part differs from the conventional design of a buckle and provides for the belt webbing a deflection point into which the belt webbing is inserted directly and becomes substantially omega-shaped during filling. This arrangement differs considerably from the conventional commercial fixing of the webbing by means of a plug-in part provided on the webbing, in particular in the form of a tongue, which is plugged into a buckle provided on the vehicle body.
It is the object of the invention to provide a three-point seat belt of the type mentioned at the outset, in which the three points ensuring guidance and fastening of the seat belt on the vehicle body when the belt is applied are equipped with conventional aids, and reliable filling of the chest/shoulder belt region and of the pelvic belt is achieved.
The gas channel which is provided in the interior of the belt, at least at a deflection point on a plug-in part which can be plugged into a buckle, in particular a plug-in tongue, can consist of a piece of hose which has relatively high rigidity in the radial direction so that the opening cross-section formed by the gas channel does not collapse when the seat belt webbing is deflected round the deflection point, but rather this opening cross-section is maintained between the pelvic belt part and the chest/shoulder belt part when the seat belt is applied, i.e. when the plug-in part, in particular the plug-in tongue, is plugged into a buckle provided for this purpose in the conventional manner on the vehicle body. In this way, a continuous flow connection is maintained through the gas channel between these two belt parts both in the situation where the seat belt is retracted into its parked or stowed position and in the applied situation. As the gas channel is arranged in the transition region between pelvic belt part and chest/shoulder belt part while allowing for the necessary dimensions of a 5th percentile woman and a 95th percentile man, the gas channel in the parked or stowed position is in the belt part which is guided substantially rectilinearly from the bottom end fitting to the deflecting fitting provided roughly at shoulder height on the vehicle. In the parked or stowed position, therefore, the gas channel is not subjected to bending stresses.
A rigid pipe elbow or a hose-like material which is preferably equipped with a reinforcing insert, in particular of helical shape, for example a helical spring, in the region of the deflection point can be used to form the gas channel. This ensures that the hose-like material forming the gas channel, when returned from the applied arrangement guided round the deflection point on the plug-in part (plug-in tongue), automatically moves into the position substantially in a rectilinear shape adapted to the belt webbing in the parked or stowed position owing to its flexibility. This can be achieved by means of a helical spring which stores the rectilinear shape mechanically. The helical reinforcement (helical spring) is preferably pressed against the internal face of the hose, which can be designed as a delivery hose for this purpose.
In a preferred embodiment, the filling gas is supplied at the end of the pelvic belt part connected to the end fitting fastened to the vehicle body. The gas supply can be formed by a gas generator, in particular a hybrid gas generator, which supplies a cold gas. However, it is also possible to design the gas supply means as a gas-tight coupling which is attached via a gas line to a gas generator, in particular a cold gas generator, for supplying a cold gas. The gas supply means (gas generator or gas-tight coupling) is preferably rigidly connected to the end fitting so that the gas supply means together with the end fitting is invariably adapted to the current strapped-in state produced on application of the seat belt.
The gas channel provided at the deflection point at one end of the pelvic belt is preferably connected to the gas supply means provided at the other end of the pelvic belt via a flexible gas line which can be formed by a flexible hose. The gas channel and the gas line can consist of a single piece of hose, wherein the hose wall can be reinforced in the radial direction by a reinforcing insert, which can preferably be a metal helix (helical spring) in the region of the deflection point to form the gas channel, as already mentioned hereinbefore.
This ensures that the chest/shoulder belt part is inflated first of all in the event of an accident. The belt interior of the chest/shoulder belt can optionally be connected to inflatable cushions which fulfil additional protective functions such as protection from lateral impacts in the head and thorax region. A rapidly increasing counter-pressure in the chest/shoulder belt part is achieved through the gas channel in the region of the deflection point between pelvic belt and chest/shoulder belt. The pelvic belt region is then filled via the gas channel and optionally via an inflated belt region at the deflection point.
Openings which are still closed during filling of the chest/shoulder belt region, in particular by the applied belt webbing fabric, can preferably be provided in the gas line which is guided through the pelvic belt part to the gas channel. Once the counter-pressure has built up in the chest/shoulder belt region owing to the filling gas (cold gas) which has entered, filling gas is blown out through the openings laterally into the pelvic belt region, the belt webbing fabric being pressed away from the openings.
The quantity of filling gas supplied by the cold gas generator can be calculated such that a holding time of about 120 ms is achieved. This holding time can be shorter or longer, depending on the requirements. If the maximum load on the occupant due to the seat belt occurs after about 60 ms in the event of an accident, it may be advantageous if the inflated seat belt is softer, i.e. the filling pressure decreases and the risk of injury is therefore reduced. With the invention, the maximum filling pressure is achieved in the inflatable belt regions after only 20 ms. Lateral impact protection is therefore also achieved, in particular, in the head region owing to appropriate dimensioning of the filling volume, in particular in the shoulder region.
An airbag cushion which is integrated in a fixed position in the inflatable pelvic belt part can optionally be provided to protect the pelvic bone. During a lateral intrusion of the vehicle structure, this airbag cushion has a protective function for a 5th percentile woman to a 95th percentile man.